3. Homeostasis Flashcards
Define Homeostasis
Homeostasis is the maintenence of a constant internal environment
Define Negative feedback control mechanism
This is when a deviation from a set point/norm value will result in effectors being activated to restore the set point value. (eg effectors being muscle or gland)
Give an example of a negative feedback control mechanism
Control of core body temperature via thermoregulation
Define positive feedback mechanism
An initial stimulus produces a response that exaggerates or enhances the change in the original conditions, rather than opposing it. I.e a deviation from the set point results in processes that enhance that deviation further from the norm
Give an example of a positive feedback mechanism
Childbirth
What are the two different systems employed in homeostatic regulation
Autoregulation
Extrinsic regulation
Define autoregulation
This describes local level, cellular/tissue level response to environmental change. Eg a change in the oxygen concentration will triger chemicals that widen/dilate blood vessels.
List the three components of a homeostatic regulatory mechanism
Receptor, detects environmental stimuli
Control center, recieves and processes information
Effector, a cell or organ which responds to commands from control centre
Define extrinsic regulation
This involves nervous/endocrine control. For example, during exercise, the nervous system issues commands to increase heart rate so blood circulates faster
Why is homeostatic regulation important
Because it is important to prevent harmful changes in body tissue fluid composition.
Define set point
This is a value at which a controlled variable should be maintained.
Define negative feedback control
aims to maintain a controlled variable at its set point. Controlled variable is some aspect of the internal environment, like blood pressure or plasma
Describe briefly the process of thermoregulation
The set point core body temperature is 37 degrees.
If temperature rises above core temp, receptors fire to the control centre.
Control centre fires to 2 target effectors.
1) Muscle tissue lining the walls of the blood vessels
2) sweat glands.
Blood vessels dilate to increase the skin surface blood flow.
Skin acts as a radiator by loosing heat to environment via sweat. Sweat evaporates.
As the set point for temp is restored, blood flow to skin returns to normal levels.
Explain the two ways in which heat loss is achieved in the event of elevated core body temperature ( >37.2 degs)
Increased blood flow to skin surface via skin capillaries.
Increased sweating
The control of body temperature can also be thought of as a thermostat. Describe this process
Set point = normal room temp
Stimulus = room temperature rises (deviation from sp)
Receptor = thermometer (detects change and sends info to control centre)
Control centre = Thermostat, sends commands to the effector to switch on
Effector = AC. unit, which turns on. effector then acts to lower the temp, and restore the room temp to within normal range.